import java.util.Scanner;

public class SynchronizedDemo {
 static class Counter {
  public int flag = 0;
 }
 public static void main(String[] args) {
  Counter counter = new Counter();
  Thread t1 = new Thread(() -> {
   while (counter.flag == 0) {
    // do nothing
   }
   System.out.println("循环结束!");
  });
  Thread t2 = new Thread(() -> {
   Scanner scanner = new Scanner(System.in);
   System.out.println("输⼊⼀个整数:");
   counter.flag = scanner.nextInt();
  });
  t1.start();
  t2.start();
 }
// 执⾏效果
// 当⽤⼾输⼊⾮0值时, t1 线程循环不会结束. (这显然是⼀个 bug)
}